Here is a necklace I made with blue accent beads and has a pewter S hook. The hook is very secure as you can pinch it shut tight after you put it on your pet. The rest of the hardware is sterling silver, and the beading wire is stainless coated with nylon, so getting it wet will not rot the necklace.
Measure your pets neck and add about an inch, you don't want the necklace to tight, as the friction from rubbing on the fur causes a static charge on the amber which also repels the ticks...